The below mentioned article provides a note on cybrid production.
In sexual hybridization process the nuclear fusion takes place between two parents, but cytoplasm is contributed by the maternal parent only. Whereas in case of somatic hybrids due to cell fusion the nucleus as well as cytoplasm derived from both the parents. But in the fusion programme it is possible to get the somatic hybrids where without nuclear fusion we can get the cytoplasmic hybrid plant only.
Here for cytoplasmic hybrid or cybrid production the fusion is done between two protoplasts where one contributes only cytoplasm, the nucleus is inactivated and as a result the cytoplasmic material or genome get mixed or hybridized but the nuclear material is contributed by one parent only (Fig. 20.8).
There are various approaches to achieve this type of fusion product or cybrids:
(i) The fusion of normal protoplast from one parent with the enucleated protoplasts from the other parent obtained by high speed centrifugation of protoplasts or by irradiation treatment.
(ii) Fusion between a normal protoplast and another protoplast which contains a non-viable nucleus (naturally produced).
(iii) Selective elimination of one of the nuclei from the fusion product just before heterokaryon formation or by selective elimination of chromosome of one parent just before first division.
Cybridisation helps to achieve the alloplasmic constitution in a single step without following the method of back-crossing for 8-12 generations. Here the alloplasmic situations are created under the control of nucleus of one parent only.
Application of cybrids would be directed to transfer the cytoplasmic male sterility character or herbicide resistance property to the recipient parent which are mainly governed by cytoplasmic genome.
Transfer of cytoplasmic male sterility character from ‘OGURA’ cytoplasm of Brassica oleracea to other species of Brassica sp. have been done successfully. Resistance to herbicide like atrazine has been transferred from Brassica campestris to B. napus by cybrid production.